On Wed, Aug 17, 2011 at 12:06 PM, Al Wick <alwick@juno.com><= /span> wrote:

<I would think that a well-designed fuel system with the pumps loca= ted as low as possible

=A0

Instead of speculations, you can actua= lly measure how good it is. A pump, clear fuel lines, and water instead of = fuel. Pinch fuel line with pliers to increase pressure drop.=A0 Watch bubbl= es come out of solution. Hear the rattle from pump due to it's inabilit= y to flow air.

If you also put a pressure gage on pum= p inlet, you can see how fine fuel filter increases risk. You can see how s= mall diameter tubing increases risk, heat, head pressure, etc etc. <= /div>

=A0

<the result of a forced landing

Egg had one forced landing. It was caused by vapor lock. Absolutely NO= THING to do with the lack of bleed line. A day later, Jan made it to the cr= ash site. Pump would not flow fuel until he cracked the line loose. This is= simply because the inlet to pumps was not wet. He did not understand this.= He just reacted to symptoms. Nothing to do with vapor lock. Remember, this= was crash site. Who knows what attitude plane was at. As I described, if y= ou screwed up your plumbing from tank to pump, then pump is not self primin= g.

=A0

<tested this system on the ground and it works as advertized
<= /div>
You also test it without the bleed line?

=A0

FWIW, everything you describe is not v= apor lock, has nothing to do with vapor lock.

=A0

-al wick

=A0

----- Original Message -----

From: Mark Steitle

To: Rota= ry motors in aircraft

Sent: Wednesday, August 17, 2011 9:1= 9 AM

Subject: [FlyRotary] Re: Dennis Have= rlah Fuel System...or any others, for that matter.

Al,

=A0

I would think that a well-designed=A0fuel system=A0with the pumps loca= ted as low as possible, in a=A0cool area,=A0and=A0a return system=A0should = not be troubled with vapor locking.=A0=A0Although I guess it could happen i= n Death Valley in=A0August if the a/c is left out in the sun for 8 hours, a= nd running auto gas.=A0 So far, I haven't had any problem here in Texas= (temps 105* today).=A0 =A0

=A0

My purpose for installing the bypass circuit was more critical to safe= flight.=A0 (The solution was=A0the result of a forced landing, or two,=A0i= n an Eggenfellner Subaru installation.)=A0 During ground runs, using a 5-ga= llon can, I found that the efi fuel pumps could not restore pressure once t= he tank had been allowed to run dry.=A0=A0When this occurred, the EFI pump= =A0would suck a big slug of air into the inlet side of the pump, loose pres= sure,=A0and being unable to build psi equal to the pressure regulator setti= ng, it would stop pumping fuel (vapor lock).=A0 The only way to restore ope= ration was to crack open the system downstream of the pump until the slug o= f air could be passed on through the fuel pump.=A0=A0Not sure this meets yo= ur definiton of "vapor lock", but I think it does, but for a diff= erent reason than fuel vapor pressure.

=A0

I have tested this system on the ground and it works as advertized.=A0= If the tank runs dry, switched to a full tank, the efi pump will restore p= ressure to the system within a few seconds.=A0 I urge all builders to run t= his test on their fuel system to determine whether or not their pumps are a= ble to restore pressure after running a tank dry.=A0 Or, just don't eve= r run a tank dry.

=A0

Mark S.

=A0

On Wed, Aug 17, 2011 at 10:22 AM, Ernest Christl= ey <echristley@att.net> wrote:

Al Wick wrote:

I'm really concerned for som= e of these fuel designs. The fuel bleed has nothing to do with vapor lock. = Virtually no effect at all.
=A0

I don't know why others are doing it, but= for me, the bleed has nothing at all to do with vapor lock. =A0Some conver= sations have been mixed together, so I can see how that could be the impres= sion. =A0The point of the pressure bleed is to bleed off the pressure after= shutdown.

I have a strong, positive head pressure going into my pumps. =A0They, a= nd the regulator, are about 8" directly below the tank. =A0Excess fuel= goes back to the opposite side of the tank from the pickup, and a single l= ine goes forward to feed the injectors. =A0The fuel lines are arranged such= that heat soaking the lines to the point of boiling the gas will push liqu= id fuel down hill and behind the firewall, isolating the gaseous gas with i= ts heat at the top of the line. =A0Turning the pumps on will pressurize the= line to 55psi, returning most of the gaseous fuel back to a liquid state. = =A0The ECM is programmed for a longer clearing pulse on hot start.

The point of the bleed is to allow fuel to move back to the tank. =A0I = had the issue of a the pressurized lines being perfectly sealed. =A0The pre= ssurized fuel was finding the path of least resistance out, which just happ= ened to be out the injector and into the intake manifold where it sat as a = little puddle. =A0Heat soaking the lines would not push liquid fuel downhil= l and back behind the firewall. =A0It would push more fuel into the manifol= d. =A0A puddle of gas sitting in a composite manifold, just above a hot exh= aust stack is just bad mojo. =A0A poorly sealed regulator allows the pressu= re to bleed off in about 5 seconds (give or take), isolating the hot fuel i= n front of the firewall, and keeping the rest cool and out of the intake ma= nifold.

Got nuthin' to do with vapor lock.

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